This invention relates to a device for heating string with the string extending as a strand travelling through the device. More particularly, the invention concerns an applicator for applying and impregnating a travelling string with a liquid, the liquid being rendered properly flowable through the application of heat.
Explaining a particular use of the device of the invention, and by this explanation it is not intended to exclude other uses where similar problems are encountered, in the manufacture of plywood, it is common to secure multiple side-by-side oriented pieces of veneer together with strings extending across the faces of the veneer and adhesively secured thereto. This renders the veneer pieces easier to handle, as when laying up a panel incorporating these veneer pieces. A string or thread commonly used in this manufacture is one impregnated with a hot-melt adhesive, such being readily secured to a veneer face by pressing the string while in a heated condition against the face of the veneer.
A number of different types of devices have been proposed for impregnating a string or thread with hot-melt adhesive. A drawback of many known devices is that they are difficult to set up with a string properly extending through the device. Some have required a needle for the purpose of so-called threading the device, but a needle is a loose article and tends to be lost. In other devices, if the string is not properly positioned, it tends to catch in the device and break. Complicating the problem is that the devices are frequently hot when being set up with string or yarn, meaning that extreme care must be used to avoid being inadvertently burned. Other problems associated with known devices are a tendency for leakage of the hot melt adhesive to occur or if adjusted to control such leakage, an insufficient amount of the hot-melt material impregnates the string being processed.
A general object of this invention is to provide a device for heating a travelling length of string or thread which is easily set up with a string extending through it, without the need to employ a needle or other aid to perform the threading process.
Another object is to provide an applicator for a thermoplastic material, such as a hot-melt adhesive, which produces good impregnation of a travelling length of string without attendant leakage of material.
A further object is to provide an applicator for applying a heated, thermoplastic material to a travelling length of string or yarn, which is easily set up or threaded with a piece of string without inadvertent breakage in the string occurring.
The applicator contemplated accomplishes uniformly good impregnation of a travelling string with such travelling at relatively high speeds. Adjustments are readily made in the applicator to accommodate the handling of different string sizes, i.e., diameters.
These and other objects and advantages are attained by the invention, which will become more fully apparent from a reading of the following description, which is to be taken in conjunction with the accompanying drawings, wherein: